RTL-SDR AIS Ship Tracking: Difference between revisions
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* tune to an AIS frequency (161.975 MHz or 162.025 MHz). the signals may not appear exactly on the AIS frequencies (the RTL-SDR is not frequency accurate (unless you have a RTL-SDR with TCXO)). Tune manually until the signals are properly centered, or set the PPM offset correctly. | * tune to an AIS frequency (161.975 MHz or 162.025 MHz). the signals may not appear exactly on the AIS frequencies (the RTL-SDR is not frequency accurate (unless you have a RTL-SDR with TCXO)). Tune manually until the signals are properly centered, or set the PPM offset correctly. | ||
* adjust the RF gain such that the signal is strong, but the noise floor is low. | * adjust the RF gain such that the signal is strong, but the noise floor is low. | ||
* use a program for decoding: AISdeco2 | * use a program for decoding: [http://xdeco.org/ AISdeco2] | ||
Revision as of 11:19, 13 June 2024
Introduction
- AIS: Automatic Identification System.
- RTL
- SDR: Software Defined Radio
- Also: ADS-B (Automatic Dependent Surveillance-Broadcast) for aircraft surveillance. 1090 MHz
Need a radio dongle, antenna. Use Arduino and RPi.
RTL-SDR V3
My dongle seems to be original, according to https://www.rtl-sdr.com/rtl-sdr-blog-v-3-dongles-user-guide/
V3 Datasheet is at https://www.rtl-sdr.com/wp-content/uploads/2018/02/RTL-SDR-Blog-V3-Datasheet.pdf
- Install the custom drivers in order to make the V4 work
- RTL-SDR Blog driver fork from https://github.com/rtlsdrblog/rtl-sdr-blog.
- Release.zip file from the Releases page. For SDR# extract the rtlsdr.dll file from the x86 folder to the SDR#. For most other x64 programs, use the rtlsdr.dll file in the x64 folder.
Software
Frequencies 161.975 MHz and 162.025 MHz. Marine VHF is narrow band (NFM) Ch16 is on 156.8MHz.
SDRSharp, SDR#
SDR#, brief tutorial:
- set your audio piping method in the Audio output drop down box
- tune to an AIS frequency (161.975 MHz or 162.025 MHz). the signals may not appear exactly on the AIS frequencies (the RTL-SDR is not frequency accurate (unless you have a RTL-SDR with TCXO)). Tune manually until the signals are properly centered, or set the PPM offset correctly.
- adjust the RF gain such that the signal is strong, but the noise floor is low.
- use a program for decoding: AISdeco2
AirSpy
Theory -- AIS decoding
https://www.rtl-sdr.com/rtl-sdr-tutorial-cheap-ais-ship-tracking/
Radio Dongle
https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/
https://www.ebay.com/str/rtlsdrblog
Antenna
The frequency of AIS signal is 161.975 MHz and 162.025 MHz, and have the max range of about 70 km. Is is a line of sight signal.
Quarter wave / dipole. One vertical 1/4 wave element connected to the center of the coax cable and 4 (or more) more grounding elements pointing towards the the ground at 45 deg. A quarter wave antenna calculator: https://jeroen.steeman.org/Antenna/Quarter-Wave-Antenna-Calculator
Coax collinear antenna. Very high omnidirectional gain. Multiple short coax cables where the outer conductor is connected to the inner conductor in an alternating fashion.
Yagi antenna. Very directional antenna that will pick up signals in the direction it is pointed: Very large gain.
Slim Jim.
Refs:
